They say blondes have more fun, but Australian actress Jessica Marais is set to wow viewers as a sultry brunette in new American cable series Magic City.

"I love the idea of breaking down any sort of stereotypes that I might have created about myself," says Marais, who became Australia's sweetheart as Rachel Rafter in long-running family drama series Packed to the Rafters.

She left the show early last year to try her luck in Hollywood and almost immediately landed a dynamite role in big-budget period drama Magic City.

The series centres on a luxury hotel in Miami Beach, Florida, in the late 1950s, a place populated by the Rat Pack, the mob and the CIA, and rife with political tensions following Fidel Castro's rise to power in nearby Cuba.

Marais plays Lily Diamond, the third (and much younger) wife of a ruthless Miami mob boss.

In the first episode the dark-haired femme fatale sizzles in a white bikini and engages in an illicit beach romp with a man who is not her husband.

Marais knows Magic City, which is produced by the same network behind the adults-only Spartacus, may shock Rafters fans.

"That was actually what attracted me to the role, partly," says the 27-year-old, who is back home in Sydney preparing for the arrival of her first child with former Rafters co-star James Stewart (Jake).

"In drama school we were encouraged constantly to play characters very far outside of ourselves and outside of our own life experience.

"Lily has a huge amount of sexual prowess and power, but she's actually very vulnerable and in quite a precarious situation with her husband. As she unfolds we realise she's a lot more intelligent and a lot more manipulative. She's a survivor."

The Logie award-winning actress who went to Los Angeles with her mother expecting to slog it out for years for her big break, but booked Magic City within weeks ("I was crying and my mum was crying ... cable television is a great place to start off a career") was unfazed by the sex and nudity in the script.

"I actually didn't feel as though any of it was gratuitous and I'm quite careful about doing nudity.

"It sometimes irritates me when I watch films and people have the sheets strategically pulled up to cover everything when there's a love scene. When people are lovers, that sort of sense of inhibition is gone.

"I thought the way [Magic City] was shot was really beautiful and quite tasteful.

"Having been in Miami and you literally see girls on the beach topless and wearing G-strings all over the place, it's sort of the backdrop for a city that is quite highly sexed and there's a heat and a sultriness to the air there. And I think it goes quite well with the show."

So, you have been warned, Rafters fans.

"Half of them will probably absolutely hate it because I don't think there's a hint of Rachel Rafter in there anywhere," Marais laughs. "But at the same time, I certainly hope that people can appreciate that it's very different and it's a nice project for me to break up the girl-next-door sort of role that I've played."

Not that she has any regrets about her time on Australia's most popular drama.

She won the role of the petulant, but beloved eldest Rafter child, in her final year of acting school and says her four years on the show, which also stars Kiwi-born actress Rebecca Gibney and Kiwi-raised actor Erik Thomson, was invaluable experience.

"I will always look back on those years as a huge amount of preparation and learning time. It was quite difficult because you're learning on the job and making mistakes and stumbling through with the audience as a performer. You're accountable for everything very publicly, which is tough.

"Having said that, I don't think anything prepared me for the scale of the production on Magic City."

The period detail has been likened to retro drama Mad Men, with more sinister subject matter.

For the role of Lily, Marais researched prominent women from the era, from the film world to the underworld, and worked with a dialect coach.

"There is a different manner of speaking, especially for women, I think, in the 1950s and 60s to modern day American accents," she says.

"Back then I think everything was a little more pointed and women were just learning to find their voice and speak out.

"I watched a whole bunch of different performances from [that time]. I really enjoyed what Kate Winslet did with her voice in Mildred Pierce and I watched real footage of people from that period to try to get the feel of it all.

"The dark hair, when you've been a notorious blonde your whole life, coupled with the make-up and the costumes as well as the accent it's very satisfying for me. It's transformational character work.

"Coming from Australia and having been doing what I've been doing for so long, it's fun to chew on something like that."

Magic City has already been renewed for a second season, which has taken some pressure of the heavily pregnant Marais, whose every doctor visit is seemingly captured by the paparazzi in her home country.

"I've sort of been locked away in my own little world Down Under," during the pregnancy, she says.

"It's all going very well. Very happy and healthy and just eagerly awaiting what's to come now."

Global star

Born in South Africa and raised in Australia, Jessica Marais can also claim a Kiwi connection.

"As a younger child my father got a job [in New Zealand] so we lived in Wellington for a while," the actress says. "I remember having earthquake drills at school. That was something that we didn't have in Australia."

Marais also starred in a few episodes of American fantasy series Legend of the Seeker, which was filmed in Auckland.

"I love New Zealand. If I could live in your part of the world I really would. Bring on the guest role in something over there! I think it's the most beautiful, diverse landscape and the people are so lovely and the crews are just a joy to work with."